I've yet to meet a socialist (yourself included) who acknowledges that there is little to no choice about driving on interstates (or public roads for that matter) and minimal choices for many about sending your kid to public school. I do like this new emerging 'in for a penny, in for a pound' thing being espoused by the socialists. I like to counter it by pointing out how much of their daily lives they effectively owe to large, multinational corporations and use this is as justification for more corporate power.
Roads are paid for by their users via taxes on fuel, tires, vehicle registration. There is little to no ability to get a 'free ride' on public roads. It's not socialism to use something you paid for.
The government has a near complete monopoly on roads. They don't have the overhead of taxes like private company would, they have the power of eminent domain to claim the property necessary for the roads, and finally they have the power of sovereign immunity to protect them from lawsuits when some moron crashes on their road and decides to blame the road's 'owner' instead of himself. This near complete lack of choice means that you can't legitimately criticize, nor can you read too much into a person's decision to use the public roads.
Public schools are funded by the state and local governments via property taxes, bonds, sales tax, income tax, etc. and without choice. You can't choose to to pay for the local school district. If you have kids, they MUST go to school. If you can't afford to pay double for each kid's education, then you'll probably send them to public schools. Again, not much room for choice for most people.
Last time I checked, nearly EVERYONE must pay for social security and medicare. Why is it wrong for me to demand to receive what I paid for?